CA1084994A - Method and apparatus for regulating electrical power delivered from an alternating current network - Google Patents
Method and apparatus for regulating electrical power delivered from an alternating current networkInfo
- Publication number
- CA1084994A CA1084994A CA286,101A CA286101A CA1084994A CA 1084994 A CA1084994 A CA 1084994A CA 286101 A CA286101 A CA 286101A CA 1084994 A CA1084994 A CA 1084994A
- Authority
- CA
- Canada
- Prior art keywords
- switching device
- consumer
- transistors
- voltage
- power switching
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M5/00—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases
- H02M5/02—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc
- H02M5/04—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc by static converters
- H02M5/22—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M5/275—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M5/293—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
-
- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05F—SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES
- G05F1/00—Automatic systems in which deviations of an electric quantity from one or more predetermined values are detected at the output of the system and fed back to a device within the system to restore the detected quantity to its predetermined value or values, i.e. retroactive systems
- G05F1/10—Regulating voltage or current
- G05F1/12—Regulating voltage or current wherein the variable actually regulated by the final control device is ac
- G05F1/40—Regulating voltage or current wherein the variable actually regulated by the final control device is ac using discharge tubes or semiconductor devices as final control devices
- G05F1/44—Regulating voltage or current wherein the variable actually regulated by the final control device is ac using discharge tubes or semiconductor devices as final control devices semiconductor devices only
- G05F1/445—Regulating voltage or current wherein the variable actually regulated by the final control device is ac using discharge tubes or semiconductor devices as final control devices semiconductor devices only being transistors in series with the load
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M5/00—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases
- H02M5/02—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc
- H02M5/04—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc by static converters
- H02M5/22—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M5/275—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M5/293—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M5/2932—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage, current or power
- H02M5/2935—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage, current or power using reverse phase control, i.e. turn-on of switches in series with load at zero crossing of input voltage, turn-off before next zero crossing
Landscapes
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- General Physics & Mathematics (AREA)
- Radar, Positioning & Navigation (AREA)
- Automation & Control Theory (AREA)
- Rectifiers (AREA)
- Dc-Dc Converters (AREA)
- Discharge-Lamp Control Circuits And Pulse- Feed Circuits (AREA)
- Ac-Ac Conversion (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A method and apparatus of regulating the electrical power delivered to a consumer from an alternating current network by adjusting the current flow angle by means of a power switching device connected in the current path to the consumer, which is switched on at the beginning of a half-wave of the network alternating voltage at a phase angle of approximately zero degrees and is switched off at a phase angle corresponding to the desired current flow angle.
A method and apparatus of regulating the electrical power delivered to a consumer from an alternating current network by adjusting the current flow angle by means of a power switching device connected in the current path to the consumer, which is switched on at the beginning of a half-wave of the network alternating voltage at a phase angle of approximately zero degrees and is switched off at a phase angle corresponding to the desired current flow angle.
Description
The present invention relates to a method of regulating the electrical power delivered to a consumer from an ~lternating current network by adjusting the current flow angle by means of a power switching device connected in the current path to the consumer, which is switched on at the beginning of a half-wave of the network alternating voltage at a phase angle of approximately zero degrees and is switched off at a phase angle corresponding to the desired current flow angle.
It is already known to effect power regulation of the described type by simply using the so-called phase angle control with thyristors or triacs as power switching devices.
In such method, during each half-wave of the network alternating voltage after the zero passage the consumer is connected thereto with such a phase angle delay that the residual phase angle of the half-wave until the next succeeding zero passage corresponds to the desired current flow angle. In particular, if the connection of the consumer bm: ~
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to the alternatin~ current network is effected at a rather large phase angle, i.e., at a relatively high instantaneous voltage of the networ~, considerable cuTrent peak values will ~i, . .................. .
occur at the instant of connection, especially for capacitive consumers. ~hese current peaks excessively losd the network and cause, in adjacent high-frequency consumers, for example radio and televi~ion apparatu~, undesirable high-frequency disturbances even when disturbance protective means are provided ~or the power switching device.
~ ~ In the United States Patent Specification 3,525,882 ¦ ~ and the British Patent Specification 1,047,904 there are alread~ disclosed power switching devices which can be connected to an alternating current network, which allow an adjustable electrical power to be delivered to the consumer ~, by arranging that, in each half-wave of the rectified but not smoothed network voltage, at the cro~s-over point of the net-,~ . .
work voltage ~semiconductor switchin~ element connected in series with the consumer is switched to the on condition and, at a predetermined, adjustable phase angle within the same half-wave, i8 again switched off. By this method th0 result i8 achieved that, upon connecting the consumer to the rectifier arrangement, which is used for rectifying the net-work alternating voltage, undesirable current peaks ars avo ded durin~ the half-~ves of t~e recOi~ied networ~
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alternating voltage, and nevertheless a free choice o~ the current flow angle is ensured during each half-wave.
For performing the above mentioned method it i8 possible, according to United States Patent ~pecification 3,525,882 to use thyristors or similar switching de~ices as the power switching means, but this demands the arrangement of ~eries connected ~ectifiers, because these thyristors do not -exhibit sufficient blocking capability under reversed polarit~
conditions. Moreover difficulties are encou~tered should a parallel connection of the thyristors be necessary to effect the power switching. Moreover, the use of thyristors as power switching devices in the inventive method is a disadvantage in 80 far as costly circuit arrangements must be provided for producing the necessary cutting off pulses.
According to British Patent Specification 1,047~904 t~e difficulties referred to can be avoided by providing as the power switching device a transistor, which is controlled by a bistable trigger circuit. Nevertheless this arrangement is not suitable for the accurate switching of large ioads at predeter-mined phase angles and with low losses because a considerable control power must be brought into effect and an unacceptably high level of heating of the transistor takes place in conse~uence of the losses. Moreover these disadva~tages may not be avoided in the known arrangement by connecting a plurality of transistors in parallel; on the contrar~ difficulties ., ' ~ ' .
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enco~tered then become even greater, particularl~ in respect of the control of the transistors. In addition ~he ~nown arrangement doe~ not permit tne transistor, which is provided as the power switching element, to switch off at a desired phase ~r~
i~ angle between 0 and 180 of the half-wave of the rectified network alternating ~oltage.
The purpose of the present invention is to provide a method of the fir~t mentioned type and a circuit arrangement for its performance, which, by the use of transistors as power switcbing elements for an alternating current delivered from an alternating current network to the consumer, will allow a loss-free and precisely timed control of.the transistors whilst avoiding unacceptab~e heating effects, even for any desired level of consumer currents, and to do this at any.
1 ~ desired time instant during each half-wave of the network ,i ~ alternatin~ ~oltage.
d ~ For solving this pro~lem, the method-of the above mentioned type is characterized in that ~here iæ employed a power switching device comprising at least two parallel connec-ted mutually decoupled transiætors, the collector-emitter paths .j; of which are connected in the current path to the consumer, and which iare alternately switched in at a switching frequency which ~;,' i5 higher than the network frequency in such manner that the time periods ol th ir IIOD~I CoDditioDs overlap and the alterrate 5- :
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switching in of the transistors t6~es place in each half ', ?
cycle of the network alternating voltage from the beginning of each half cycle until the desired current flow angle is ,. .. ..
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~he control of the transistors is ef*ected preferably each case by a transformer in order that the control power may be kept low, Advantageously each transistor is co~trolled by a control voltage applied to the primary side of each ~;- transformer and having an at least approximately recta~gular wave form of gated pulses and gated space intervals, ~aid intervals each includine a wave segment, the polarity of which - is opposite to that of the gated pulses iu order to render - the remanence o$ the transformer ineffective.
According to a variant Or the method of the invention, by the use of a second power switching device the consumer - c~n be damped Pnd discharged in each half-wave of the net-, ~ork alternating voltage, in which ca~e the second power switching devico becomes effecti~e after each interruption of the connection of the consumer to the networ~ has been brought ~bout by switching out the first power switching device, and said ~econd power switc~i~g de~ice becomes inef~ective before every reconnectio~ of the consumer with the networ~ brought ~bout by the switching in of the first power switchi~g de~ice. -6. ~' ~ ~' ' , .
This variation of the method makes it possible by the periodic connection of the comsumer to the alternating current network in the zero cross-over point of the network alternating voltage, to bring about in the consumer at least substantially complete discharge approximat~ng to the ideal condition. By these means it becomes possible to avoid the risk of formation of current peaks at the instant of connection, this resulting on the one hand in the avoidance of high frequency disturbance effects and furthermore the avoidance of over-loading the netwark switching device effecting the connection of the consumer to the network.
Accordingly, in the above described variant of the method the second power switching device, which damps and discharges the consumer, becomes effective when the first power switching device, which connected the consumer to the alternating current netw~rk, is ineffective. ~hus it is possible for the energy stored in the consumer to be discha~ged through the consumer and through the second power switching device, whilæt said second device is effective, in the time interval before the next reconnection of the first power switching device at the next zero crass-over point of the network alternating voltage, so that at the time instant of the said reconnection not only is there no ~oltage at the terminals of the consumerr but also there is no electrical or mechanical energy stored in the consumer. m erefore no current peaks can be established upon reconnection of the bm: ' .
'' ~ ~084994 consumer to the alternating current network.
An advantageous practical form of the described variant of the m~thod provides that in the second power switching device at least one transistor is used, whose collector-emitter path is arranged in a current path lying parallel to the consumer, which transistor is switched on and switched off in a time interval occurring between the interruption of the connection and the reconnection of the consumer with the network, this switching being effected at a switching frequency which is higher than the network frequency, whilst the switching off period of the transistor occurs during a time which is shorter than the storage time of the transistor. Having regard to this storage time, it is advantageous to employ a Darlington transistor, the cost of which is, nevertheless, only slightly higher than that of a conventional transistor. Darlington transistors exhibit at the present time storage periods of about 15 to 20 microseconds, 80 that the storage effect of the Darlington transistor can be utilized for bridging over the gated space intervals.
In order that the power applied in controlling the transistor can be kept small, it is advantageous to employ for controlling the transistor a control voltage having an at least approximately rectangular characteristic, and to deliver this to the transistor through a transformer.
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In the performance of the above defined inventive method ~............................................ . .
there is employed a circuit arrangement characterized by the feature that the first mentioned power switching device comprises at least an arrangement of two transistors connected in series to the consumer and having parallel coDnected collector-emitter paths, together with an arrangement of rectifiers ror correct polarity delivery of the network ., - .
alternating voltage, wherein there iP connected in the base-emitter circuit of-each transistor the secondar~ winding of a~ associated transformer, the primar~ winding of which is connected to a circuit arrangeme~t for generating the control voltage for the transistors.
~or performing the above described variant of the method7 the inventive circuit arrangement may contain, connected in parallel to the consumer, a second power switching device, which comprises the series circuit of the collector-emitter path of a transistor, e.e. a Darlington transistor~ further-more an arrangement of rectifiers for correct polarity delivery to the transistor of the voltage applied to the consumer, and a load, whilst in the base-emitter circuit of the transistor there is connected the secondary winding of a transformer, the primary ~Ji~ding of which is connected to a circuit arrangement for generating the control voltage for the tra~sistor.
An advantageous practicaljform of this circuit arrangement consists of rectifiers arranged in a rectifier . . , -. ' :' ~ ' r `
bridge, one diagonal of which is connected parallel to theconsumer, and to the other diagonal of which there is connected the collector-emitter path of the transistorO
For the purpose of receiving the stored energy upon discharge of the consumer, the load which is connected in ~ parallel to the consumer may be an ohmic resistance and a choke.
- ~he herein~described methods and circuit arrangements can be applied for the regulat~on of any desired t~pes of consumer driven by an alternating current network, in particular those of a highly capacitive character or those with exceptionally reflective characteristics, as well as consumers with reactive load compensation.
An important application of the invention consists in the regulation of the brilliance of an electrical li~hting irlstallation. In particular the method can advantageously be u~ed for the regulation of fluorescent tubes in a lighting installation whilst having only the slightest interference with an existing system, and bringing with it optimal compensation of the reactive power and small regulating losses. In particulax the above de~ined discharge of the total consumer network pxo~ides constant conditions at the start of each half-wave and diminishes the ris~ of extinction by the suppression of random glow discharges through participating starters during the transient decay process, such as would occur in the a~sence of this switching device for discharge ~nd damping.
1~84994 A further field of application is the regulation of the driving powers of electric motors. In this field the ab.sence of high peak current values when employing the inventive met~lod means that t~ere .is a reduction in the ~tressing of the internal motor insulation caused by parasitic capacitances, in contrast to the conditions obtaining when the known regulation b~ phase angle contrcl is employed, as well as a reduction i~ the bearing ~tresses due to pe~k ~orques.
I~ particular, in consequence of the above defined discharge of the consumer, there is achie~e~, on account of the absence Or a change of current direction, ~Jh~ch wov.ld othelwise inevitably result from the transient eff~cts following the switching off of the network switching device for current ~upply, an optimal integration of the impressed current in the motor and therefore an added improv~ment in the steady running behaviour of the motor.
In accordance with one aspect of the present invention there is provided a method of regulating electrical power supplied via a current path to at least one consumer in an A.C. network which involves setting desired current flow angle using a power switching device connected in the current path to the consumer, the improvement comprising providing as the switching device at least two transistors, connected in parallel and mutually decoupled, connecting collector-emitter leads of the transistors in the current path to the consumer, switching the transistors alternately at a switching frequency higher than the line frequency in such j rr ~
-, - '- ' ~ . ' ~ , . , ^` 1C~84~94 manner that the time intervals of their ON states overlap cutting the switching device ON at the beginning of each half wave of A.C. line voltage, at least approximately at a phase angle of 0 , and cutting the power switching device OFF at a phase angle corresponding to the desired current flow angle; whereby the alternate connection of the transistors takes place in each half period of the A.C. line voltage beginning at its start and lasting until the desired cuTrent flow angle is reached.
According to another aspect of the present invention, there is provided a method of polarity-independent reduction of feedback from a consuming means periodically connected to an A.C, line which includes disconnecting the consuming means from the line during a predetermined period in each half wave of the A.C. line voltage, the improvement including damping and dis-charging the consuming means during each half wave of the A.C, line voltage using a power switching means during the predetermined period when the consuming means is disconnected from the A.C, line.
Further applications of the invention are possible in the field of electrical ignition for combustion processes.
Practical examples of the inventive method and of circuit arrangements for its performance will no~ be described in more detail with reference to the accompanying drawing, in which:
Fig. 1 is a diagram of current plotted against time in a consumer when using the known method of regulation by phase angle control, - llA -jrr:~rc .
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Fig. 2 is a diagram of the current plotted against time in a consumer when using the inventive method o~ regulation, Fig. 3 is a circuit diagram of a first practical form of the power switching device for performing the inventive method, ~ig~ 4 is a diagram of the control voltages as a function of time i~ respect of the power switch-ing device of fig. 3, Fig. 5 i~ a circuit diagram of a second practical form - of the power switching device, Fig. 6 i~ a diagram of the current consumption plotted with respect to time in a consumer with periodic interruption of the consumer from the alternating current network and respective reconnection of the consumer with the network, when the consumer has stored electrical energy, i.e. in the case of a complex consumer, Fi~. 7 is a diagram of the voltage established at a complex consumer plotte~ as a function of time, : Fig 8 i8 a diagram of the voltage established at a complex consumer plotted as a ~unction with - respect to time when using a variant of the inventive method, 12.
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Figo 9 is a circuit diagram of an arrangement for regulating the brilliance of a lighting installation having a second power switching device for performin~ the variant o~ the met~od of the invention, Fig. 10 is a diagram showing the control pulses used i~ the arrangement of fig. 9 plotted with respect to time.
I~ fig. 1 there is shown as a function of time the current flowing through a consu~er according to a known method Or regulation by phase angle control. ~rom the first zero cross-over point tO up to a later time instant tl the rele~ant power switching device remains blocked, i.e. no current flows.
At the time instant tl the power switching device is switched on, i.e. the consumer is connected to the network, so that a sudden current increase takes place at a high velocity, which c~uses the already described current peaks and high frequency disturbances to occur. The current continues to flow until the next zero cross-over point tO'.
` Fig. 2 show~ the correspo~ding current graph with respect to time in a method of regulation in accordance with the invention. ~he appertaining power switching device is here already switched on at the time instant tO of the first zero cross-over point, so that the network alternating current already flows through the consumer from the instant o~ c~oæs-f 13- i ~ }
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over of the alternating voltage, and the sudden ~rrent surge is avoided. At a later time instant t2, corresponding to the desired current flow angle, the power switching device i8 blocked so that the current flowing through the consumer sinks to zero until the power switching device is again switched on at the next zero transit.
In the practical e~ample represented in fig. 3 a consumer V is connected through a power switching device L~l to terminals N of an alternating current network. The power switching device ~Sl comprises two transistors Tl and '~2, which are mutually decoupled in parallel connection in that the~ respective collectors and emitters are connected together. The connected collectors and emitters of the transistors Tl and T2 are conneçted across one diagonal of a rectifier bridge Gl, which has in each branch a rectifier Dl, D2, D3 and D4 respectively, for example one or more diodesO
~he other diagonal of the rectifier bridge i8 connected in series with the consumer V. ~he rectifier bridge serves the purpose of protecting the transistors from faulty poling and to make possible the full-wave operation of thé power switching device here shown.
For the purpose of controlling th~ tra~sistthrs ~ and ~2 the bases thereof are connected in each case / a current limiting resistance Rl and ~2 to the secondary wind~ng of a .
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~ ~ f`` - ` 1084994 driver transformer TRl and TR2 respectively. To the primary windings of the respective transformers there are delivered control voltages Ul and U2, which will be further described herein, ~or which purpose the primary windings are connected to ~eparate output terminals of a control voltage generator SGl.
The control of the transistors ~1 and T2 throu~h the trans-formers makes it pos~ible by the use of impedance matching to keep the necessar~ control power low; this method of control also makes possible a potential separation of the bases of the two transistors. In~tead of using two transistors Tl a~d ~2 it i8 also possible, in accordance with the loading, to pro~ide a greater number of transistors connected in parallel in the same manner.
With the object firstly of obtaining precise switching instant~ for the transistors Tl and T2, and thereby to achie~e a precisely determined current flow angie, and secondly in order to keep the dimensions of the driving tr~nsformers ~Rl ~nd TR2 small, the control voltage generator SGl i8 80 designed that it delivers at it~ output terminals control signals, the frequency of which is substantially higher than that of thé
network frequency, and amounts for example to around 10 k~z.
~he con~trol signals are also preferably ~t least approximately rect~ngul~r, whilst the control signals delivered at the two respecti~e output pairs of terminals of the control signal generator SGl are mutually displaced in time but overlap each other.
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The control ~oltages Ul and U2, which are preferabl~
delivered by the control voltage generator SGl, are represented schematically in fig. 4 as a function of the time.
~he control voltage Ul is a re~tangular voltage with gating pulses I and spacing intervals L, in which the control voltage falls to zero value~ However, within the space intervals L
there are provided~ additional pulses Z, the polarity of which' is opposite to those of the gating pulses I. The control voltage U2 exhibits the same time characteristic as the control voltage Ul, but i8 time displaced with respect to it so that the gating pulses I of the control voltage U2 occur at the same time as the space intervals L of the control voltage Ul. As will be seen from fig. 4 the gating p~lses I of the control voltages Ul and U2 overlap ~ach other during the time period ~t.
~ he mode of operation of the power switching device of-fig. 3 i8 as follows, assuming as a basis the signal voltages ~1 and U2 of fig. 4.
At the beginning of a half-wave of the ~etwork altern~-ting voltage (phase angle e~ual to zero degree~) the control ~ generatorvoltage'~Gl i8 opened and delivers control voltages Ul and U2 to the primary windings of the driving transl'ormers TRl and TR2 respectively. Initially there is delivered through the one transformer, e.g. the transformer ~1, the control voltage Ul, with the gating pulse I, to the transistor ~1, so that the latter becomes current don'ducting. Before the beginning of the 16.
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saturation of the tra~sformer T~l the gating pulse I of the control voltage U2 is delivered by transformer TR2 and brings the transistor T2 into the current conducting condition, and indeed this happens during the time that the transistor Tl i8 still current conducting on account of the overlapping of the control voltages Ul and U2, so that in the consumer V there i~
obtained a continuous current flow. The space interval L
of the control voltage Ul now blocks the transistor ~1, whilst the additional pul~e Z of reverse polarity occurring within that interval removes the remanent mag~etization in the transformer, and thus increase~ the power capability for the next succeeding current conducting phase of the transistor ~1.
This operation repeats itself alternately for the transistors Tl and ~2, 80 that the loading distributes itself uniformly over the two participating transistors Tl and T2, whilst the current flowing through the consumer V ass~mes continuously the course of the network alternating voltage in the respective half-wave. For achieving the de~ired current flow angle, the control voltage generator SGl is then blocked~at the correspon-ding phase angle of the half-wave, 80 that a fuxther control of the transistors ~1 and T2 into t e current conducting condition is omitted until the beginning of the next half-wave of the network alternating voltage. The diodes Dl to D4 of the rectifier bridge Gl here provide for the correct poling in accordance with the alternating sign of the half-waves.
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In an e~ample the pulse frequency of the control ~oltages ~1 and U2 was lO kHz, the voltage of the gated pulses +lOV, the voltage of the additional pulses -lO V, and the transforma-tion ratio of the transformers ~Rl and T~2 was 3 ~ l. The ,;"
~ generation of the control voltages Ul and U2 as well as the .~,.................................................................... .
adjustment of the desired current flow angle by the starting and bloc~ing of the control voltage generator SGl can quite easil~ be effected with ~nown means, in particular by means of digital circuit arrangements.
A further practical form Or the power switching de~ice, which is capable of switching a larger current and which generates a smaller thermal loss is represented in fig. 5.
In the power switching device LS2 here shown there are provided two arrangements o~ decoupled parallel connected transistors T3, T4 and T5, T6 respectively, ths control of which i~ effected, as in the practical example of rig. 3, by the individually allocated driving transformers TR3, TR4, TR5 and TR6, together with current limiting resistances R3, R4, R5 and R6. For achieving the correct poling for a full-wa~e d~i~ing operation, a rectifier D5 and D6 respectively, e.g. a diode, i8 connected in series to each arrangement T~3, TR4 and TR5, TR6 of parallel connected transistors. ~hese two series circuits are connected in parallel and are situated in the current path of the network in series with the consumer V, so that the current ~low directions of the arrange~ent~ of the transistors and the . ,, /
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rectifier1 with reference to the network or consumer connection side of the said parallel circuit, are opposite to each other in the one branch and the other br~nch of the parallel circuit.
~he primary winding~ of the transformers TR3 to TR6 are connected to suitable output terminals of a control ~oltage generator SG2 *or delivering the appertaining control voltages U3, U4, U5 and U6 The course taken b~ the control voltages U3 to U6 aiffers from that of the control voltages U2 and ~3 of ~ig. 3 ~olely by reason of the fact that, in dependence upon thé existing polarity of the network alternating voltage, the control can be discontinued of that particular arrangement of transistors T3, ~4 or ~5, ~6 respectively which happens to be in the non-loaded condition.
In the practical example of fig. 5 thermal losses occur only at two rectifiers D~, D6. Moreover the current loading distributes itself over four transistors ~3 to T6.
! In the described methods and circuit arrangements it is conceded that at the t~me instant of disconnection any stored electrical or magnetic energy will cause transient oscillation ahd will be dissipated in the consumer. In such a case it is to be expected that a voltage pea~ will occur. Because in most cases the consumer load will include both inducti~e and capacitive components, it will also not be possible to avoid change~ of curre~t direction in the consumer. ~urthermore it is ~ecessary to have regard to parit~ between the electrical .' 19.
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~` 1084994 condition in the consumer and in the network when the current supply to the consumer iB renewed~ because otherwise it must be expected that additional current peaks will result.
In fig. 6 there is shown, on a basis corresponding to that of fig. 2, the time function of a current taken by a consumer from a~ alternating current network, wherein the consumer is connected to the network in each half-wave at the zero cross-over point of the network alternating voltage, i.e. at the time instants tO, t2, t4 etc, and/co~nected fro~
the network at a later time instant tl, t~, t5 etc. corres-ponding to the desired current flow angle. It can be shown that, in consequence of the storage of energy, strong current peaks will occur at each reconnection of the consumer ~th the network at the time instants tO, t2, t4 etc., as indicated in fig. 6. Such current peaks cause considerable high frequency disturbing voltages, and moreover place a load on the switch-ing device which is used for effecting the discon~ection and reconnection of the consumer with the network, the switching element of said switching device usually being in the form of a semiconductor arrangement which i8 sensitive to current a~d voltage peaks.
The cause of the voltage peaks of fig. 6 is shown in fig. 7, which indicates the corresponding time function o~ the voltage at the consumer. ~he consumer is disconnected from 20.
, ' :~ - -1~84994 the network at the time point tl. In consequence of energy storage, the voltage at the consumer then falls off, for example in accordance with the full line of the curve and tends to continue a course along the dashed line. Because, at the time instant t2, at the zero cross-over point of the net~rork alternating voltage a reco~nection of the consumer with the networ~ iæ established, the decay process must ~e interrupted and the voltage at the consumer must of necessity follow the network voltage. The corresponding surge in the consumer voltage indicated at the time instant t2 in fig. 7, from a value differing from zero value to a practically zero value in the zero cross-over point of the network alternating voltage, gives rise to the current pea~ shown in fig.6 at the time instant t2 as well as at the corresponding time instants t4 etc. at the beginn;ng of a new commutation phase.
According to a variant of the inventive method, at all of the time instants tl, t3~ t5 etc. or shortly thereafter, i.e. after the disconnection of the consumer from the network, the consumer i8 damped a~d its energy content substantiall~
short circuited. ~he mode of operating this method i8 shown in fig.8. From this it ls clear that, as a result of the imposed damping and discharge beginn~ng from the time i~stants tl, t3, t5 etc., the voltage assumes a strongly attenuated course, so that at the time insta~ts t2, t4 etc., at which the consumer is reconnected to the network, the voltage has f 21.
-"` 108~994 practicall~ assumed the zero value. The current taken by the consumer from the network therefore no longer exhibit~
the current peaks at the time instants t2, t4 etc. shoh~ in fig.6, but in other respects t~kes the form of fig.6.
In fig. 9 there is shown schematically an arrangement for regulating the brilliance of a lighting installation. In this arrangement the consumer, which is conn~cted through a f~r~t power switching device to the terminals ~ of an alternating current network comprises a plurality of ballast devices V& and a pluralit~ of fluorescent tubes I~, of which only one of which i8 shown in the drawing, as well as the appertaining glow starter GS. ~he first power switching device is the same as the ~ower switching device LSl of fig.3 and therefore contains the rectifier bridge Gl with the four diodes Dl to D4 and the two transistors T1 and ~2, whose respectively connected collectors and e~itters are connected to one diagonal of the rectifier bridge Gl. ~he other diagonal i8 connected through two windings Wl and W2 of a choke D~ in series to the above mentioned con~umer. The choke windings Wl and W2 together with the parallel connected condensers Cl and C2 fu~ction both as disturbance protective members as well as protective means for the sem~conductor elements present in the illustrated arrangement.
For the purpose of controlling the transistors Tl and ~2, the ~ases thereof ar~, like those in fig. 3, connected 22.
1~84994 through current limiting resistances Rl, R2 and driving trans~ormers ~Rl, TR2 to a con~rol voltage generator SG3, which delivers the control voltages Ul and U2. The graph o$
the control voltages ~1, U2 has already been described with reference to fig.4 and is again shown in fig.10.
A second power switching device for periodically damping and discharging the consumer contains, according to fig.9, a ~urther rectifier bridge G2 with four diodes ~7 to D10, one diagonal of which rectifier bridge is connected through a limiting and load resistance R7, as well as through a further winding W3 of the choke D~, parallel to the consumer containing the ballast devices YG and the fluorescent tubes ~R. I~ the other diagonal of the rectifier bridge G2 there is connected the collector-emitter path of a Darlington transis-tor T7, whose base i8 connected through a current limiting resistacce R8 to the secondary winding of a further driving transformer TR7. ~o the primary winding Or the tr~nsformer ~7 there i8 delivered a control voltage U7, for which purpose the ilatter is connected to further output terminals of the control voltage generator SG3. ~he control voltage U7, like the control voltages Ul and U2, i8 rectangular and has a sub-stantially higher frequency as compared with the network frequenc~. Preferably the control voltage U7 exhibits the ~ame shape and frequency as the control voltages Ul and U2, as is represented in fig.10, but the control voltage ~7 contains no i, , 23. `
108499~
additic-al pul~as of opposite polarity. As will be fieen in fig.10 and will be further described later, the control volta~e ~o~orator SG3 periodically delivers the control voltage U7 at times when there is no delivery of control voltage~ Ul and U2 from the control voltage generator SG3.
At the beginning of a half-wave of the network alternatin~ vol~age (phase angle equal to zero degrees corresponding to the time insta~ts tO, t2, t4 etc. in fig.8) the control voltage generator SG3 delivers the control voltages Ul and U2 to the primary windings of the driving transformers TRl and TR2, as is alread~ described with reference to fig. 3. For obtaining the desired current flow angle, the control voltage generator SG3 then interrupts, at the corresponding phase angle of the half-wave, corresponding to the time instants tl, t3, t5 etc. in ~ig. 8, the delivery of the control voltages Ul and ~2, 80 that a further control Or the transistors Tl and T2 into the current conducting condition is suspended until the beginning of the next half-wave. The diodes Dl to D4 of the rectifier bridge Gl provide in this case for the correct poling in correspondence with the alternating sign of the half-waves.
~ llowing for a slight delay taking into aocount the storage and discharge times of the semconductor eleme~ts, the control voltage generator SG3 delivers, following the last pulse of the control voltages ~1, U2, and within the same . .: : ..
1(~84~94 half-wave, the rectangular control voltage U? (fig.10) so that the Darlington transistor T7 becomes current conducting.
Because the pulse gap~ of the control voltage U7 are smaller than the storage time of the Darlington transistor T7, the current conducting condition o$ the transistor T7 is continuous.
~he time period during which the transistor T7 is in the conducting condition provides, throu B the rectifier bridge G2, i e. the diodes D7, D9 or D8, D10 according to the polarity of the respective half-wave, the load resistance R7 and the winaing W3 of the choke DR, a current path parallel to the consumer. Accordingly it is possible for the electrical energy stored in the consumer to diæcharge continuously through the Darlington transistor ~7, th;s being i~dicated in fig.9 by the condenser C3 shown in dashed lines indicating a compen-sating and parasitic capacitance.
: As is evident from fig.10, the control voltage generator SG~ interrupts the delivery of the contro} volta~e U7 shortly before the next zero cross-over point of the network alternating voltage, i.e. shortly prior to the instant whe~ the control voltage generator SG3 again brings the transistors Tl and T2 alternately into the conducting condition by mean~ of the control ~oltages Ul and U2.
In the reconnection of the consumer to the network after the completion of periodic separatio~ from the network, the ` 25.
, , , ' ' ~ ~ ~ ' '.
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- . , 1~84994 suppression of current peaks, which is effected by the described discharge of the complex consumer for the purpose of power regulation i8 indeed involved with losses, but the~e are nevertheless acceptable and are not signific~nt as co~- -pared with the achieved advantage of the avoidance of current peaks ~or example the arrangement represented in fig.9 may be for the regulation of a fluorescent tube lighting installa-tion, which is designed for a nominal current of 35 A, and which includes for complete compensation of the fluorescent tubes a parallel capacitan¢e of 450 microfarads. This capacitance will, in the most un*avourable case, be charged to ~ voltage of 300 V, 80 that for each half-wave an energy of 135 mWs i8 to be expended, because the residual component in the *orm of non-capacitively ~tored energy is dis~ipated through the ballast deYices and~the fluorescent tubeY. ~he total efficiency of the arrangement shown in fig.9 is there-fore degraded by only 1.7%.
~ he oontrol of the transistors Tl, T2, ~7 through trans-rormers makes it possible to maintain the necessary control power small by impeda~ce matching. Furthermore this method makes po~sible the potential separation of the bases of the transistors. ~he generation of rectangular control signals ~1, ~2, U7 having a substantially higher frequency than that of the network can, as shown, be effected by a single control vol-tage generator SG3, 80 that the latter can ~e of relatively ~imple design.
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It is already known to effect power regulation of the described type by simply using the so-called phase angle control with thyristors or triacs as power switching devices.
In such method, during each half-wave of the network alternating voltage after the zero passage the consumer is connected thereto with such a phase angle delay that the residual phase angle of the half-wave until the next succeeding zero passage corresponds to the desired current flow angle. In particular, if the connection of the consumer bm: ~
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to the alternatin~ current network is effected at a rather large phase angle, i.e., at a relatively high instantaneous voltage of the networ~, considerable cuTrent peak values will ~i, . .................. .
occur at the instant of connection, especially for capacitive consumers. ~hese current peaks excessively losd the network and cause, in adjacent high-frequency consumers, for example radio and televi~ion apparatu~, undesirable high-frequency disturbances even when disturbance protective means are provided ~or the power switching device.
~ ~ In the United States Patent Specification 3,525,882 ¦ ~ and the British Patent Specification 1,047,904 there are alread~ disclosed power switching devices which can be connected to an alternating current network, which allow an adjustable electrical power to be delivered to the consumer ~, by arranging that, in each half-wave of the rectified but not smoothed network voltage, at the cro~s-over point of the net-,~ . .
work voltage ~semiconductor switchin~ element connected in series with the consumer is switched to the on condition and, at a predetermined, adjustable phase angle within the same half-wave, i8 again switched off. By this method th0 result i8 achieved that, upon connecting the consumer to the rectifier arrangement, which is used for rectifying the net-work alternating voltage, undesirable current peaks ars avo ded durin~ the half-~ves of t~e recOi~ied networ~
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alternating voltage, and nevertheless a free choice o~ the current flow angle is ensured during each half-wave.
For performing the above mentioned method it i8 possible, according to United States Patent ~pecification 3,525,882 to use thyristors or similar switching de~ices as the power switching means, but this demands the arrangement of ~eries connected ~ectifiers, because these thyristors do not -exhibit sufficient blocking capability under reversed polarit~
conditions. Moreover difficulties are encou~tered should a parallel connection of the thyristors be necessary to effect the power switching. Moreover, the use of thyristors as power switching devices in the inventive method is a disadvantage in 80 far as costly circuit arrangements must be provided for producing the necessary cutting off pulses.
According to British Patent Specification 1,047~904 t~e difficulties referred to can be avoided by providing as the power switching device a transistor, which is controlled by a bistable trigger circuit. Nevertheless this arrangement is not suitable for the accurate switching of large ioads at predeter-mined phase angles and with low losses because a considerable control power must be brought into effect and an unacceptably high level of heating of the transistor takes place in conse~uence of the losses. Moreover these disadva~tages may not be avoided in the known arrangement by connecting a plurality of transistors in parallel; on the contrar~ difficulties ., ' ~ ' .
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enco~tered then become even greater, particularl~ in respect of the control of the transistors. In addition ~he ~nown arrangement doe~ not permit tne transistor, which is provided as the power switching element, to switch off at a desired phase ~r~
i~ angle between 0 and 180 of the half-wave of the rectified network alternating ~oltage.
The purpose of the present invention is to provide a method of the fir~t mentioned type and a circuit arrangement for its performance, which, by the use of transistors as power switcbing elements for an alternating current delivered from an alternating current network to the consumer, will allow a loss-free and precisely timed control of.the transistors whilst avoiding unacceptab~e heating effects, even for any desired level of consumer currents, and to do this at any.
1 ~ desired time instant during each half-wave of the network ,i ~ alternatin~ ~oltage.
d ~ For solving this pro~lem, the method-of the above mentioned type is characterized in that ~here iæ employed a power switching device comprising at least two parallel connec-ted mutually decoupled transiætors, the collector-emitter paths .j; of which are connected in the current path to the consumer, and which iare alternately switched in at a switching frequency which ~;,' i5 higher than the network frequency in such manner that the time periods ol th ir IIOD~I CoDditioDs overlap and the alterrate 5- :
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` :~084994 , ~
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switching in of the transistors t6~es place in each half ', ?
cycle of the network alternating voltage from the beginning of each half cycle until the desired current flow angle is ,. .. ..
.Z,~, , reac~ed.
~he control of the transistors is ef*ected preferably each case by a transformer in order that the control power may be kept low, Advantageously each transistor is co~trolled by a control voltage applied to the primary side of each ~;- transformer and having an at least approximately recta~gular wave form of gated pulses and gated space intervals, ~aid intervals each includine a wave segment, the polarity of which - is opposite to that of the gated pulses iu order to render - the remanence o$ the transformer ineffective.
According to a variant Or the method of the invention, by the use of a second power switching device the consumer - c~n be damped Pnd discharged in each half-wave of the net-, ~ork alternating voltage, in which ca~e the second power switching devico becomes effecti~e after each interruption of the connection of the consumer to the networ~ has been brought ~bout by switching out the first power switching device, and said ~econd power switc~i~g de~ice becomes inef~ective before every reconnectio~ of the consumer with the networ~ brought ~bout by the switching in of the first power switchi~g de~ice. -6. ~' ~ ~' ' , .
This variation of the method makes it possible by the periodic connection of the comsumer to the alternating current network in the zero cross-over point of the network alternating voltage, to bring about in the consumer at least substantially complete discharge approximat~ng to the ideal condition. By these means it becomes possible to avoid the risk of formation of current peaks at the instant of connection, this resulting on the one hand in the avoidance of high frequency disturbance effects and furthermore the avoidance of over-loading the netwark switching device effecting the connection of the consumer to the network.
Accordingly, in the above described variant of the method the second power switching device, which damps and discharges the consumer, becomes effective when the first power switching device, which connected the consumer to the alternating current netw~rk, is ineffective. ~hus it is possible for the energy stored in the consumer to be discha~ged through the consumer and through the second power switching device, whilæt said second device is effective, in the time interval before the next reconnection of the first power switching device at the next zero crass-over point of the network alternating voltage, so that at the time instant of the said reconnection not only is there no ~oltage at the terminals of the consumerr but also there is no electrical or mechanical energy stored in the consumer. m erefore no current peaks can be established upon reconnection of the bm: ' .
'' ~ ~084994 consumer to the alternating current network.
An advantageous practical form of the described variant of the m~thod provides that in the second power switching device at least one transistor is used, whose collector-emitter path is arranged in a current path lying parallel to the consumer, which transistor is switched on and switched off in a time interval occurring between the interruption of the connection and the reconnection of the consumer with the network, this switching being effected at a switching frequency which is higher than the network frequency, whilst the switching off period of the transistor occurs during a time which is shorter than the storage time of the transistor. Having regard to this storage time, it is advantageous to employ a Darlington transistor, the cost of which is, nevertheless, only slightly higher than that of a conventional transistor. Darlington transistors exhibit at the present time storage periods of about 15 to 20 microseconds, 80 that the storage effect of the Darlington transistor can be utilized for bridging over the gated space intervals.
In order that the power applied in controlling the transistor can be kept small, it is advantageous to employ for controlling the transistor a control voltage having an at least approximately rectangular characteristic, and to deliver this to the transistor through a transformer.
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F~ 84994 .~
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In the performance of the above defined inventive method ~............................................ . .
there is employed a circuit arrangement characterized by the feature that the first mentioned power switching device comprises at least an arrangement of two transistors connected in series to the consumer and having parallel coDnected collector-emitter paths, together with an arrangement of rectifiers ror correct polarity delivery of the network ., - .
alternating voltage, wherein there iP connected in the base-emitter circuit of-each transistor the secondar~ winding of a~ associated transformer, the primar~ winding of which is connected to a circuit arrangeme~t for generating the control voltage for the transistors.
~or performing the above described variant of the method7 the inventive circuit arrangement may contain, connected in parallel to the consumer, a second power switching device, which comprises the series circuit of the collector-emitter path of a transistor, e.e. a Darlington transistor~ further-more an arrangement of rectifiers for correct polarity delivery to the transistor of the voltage applied to the consumer, and a load, whilst in the base-emitter circuit of the transistor there is connected the secondary winding of a transformer, the primary ~Ji~ding of which is connected to a circuit arrangement for generating the control voltage for the tra~sistor.
An advantageous practicaljform of this circuit arrangement consists of rectifiers arranged in a rectifier . . , -. ' :' ~ ' r `
bridge, one diagonal of which is connected parallel to theconsumer, and to the other diagonal of which there is connected the collector-emitter path of the transistorO
For the purpose of receiving the stored energy upon discharge of the consumer, the load which is connected in ~ parallel to the consumer may be an ohmic resistance and a choke.
- ~he herein~described methods and circuit arrangements can be applied for the regulat~on of any desired t~pes of consumer driven by an alternating current network, in particular those of a highly capacitive character or those with exceptionally reflective characteristics, as well as consumers with reactive load compensation.
An important application of the invention consists in the regulation of the brilliance of an electrical li~hting irlstallation. In particular the method can advantageously be u~ed for the regulation of fluorescent tubes in a lighting installation whilst having only the slightest interference with an existing system, and bringing with it optimal compensation of the reactive power and small regulating losses. In particulax the above de~ined discharge of the total consumer network pxo~ides constant conditions at the start of each half-wave and diminishes the ris~ of extinction by the suppression of random glow discharges through participating starters during the transient decay process, such as would occur in the a~sence of this switching device for discharge ~nd damping.
1~84994 A further field of application is the regulation of the driving powers of electric motors. In this field the ab.sence of high peak current values when employing the inventive met~lod means that t~ere .is a reduction in the ~tressing of the internal motor insulation caused by parasitic capacitances, in contrast to the conditions obtaining when the known regulation b~ phase angle contrcl is employed, as well as a reduction i~ the bearing ~tresses due to pe~k ~orques.
I~ particular, in consequence of the above defined discharge of the consumer, there is achie~e~, on account of the absence Or a change of current direction, ~Jh~ch wov.ld othelwise inevitably result from the transient eff~cts following the switching off of the network switching device for current ~upply, an optimal integration of the impressed current in the motor and therefore an added improv~ment in the steady running behaviour of the motor.
In accordance with one aspect of the present invention there is provided a method of regulating electrical power supplied via a current path to at least one consumer in an A.C. network which involves setting desired current flow angle using a power switching device connected in the current path to the consumer, the improvement comprising providing as the switching device at least two transistors, connected in parallel and mutually decoupled, connecting collector-emitter leads of the transistors in the current path to the consumer, switching the transistors alternately at a switching frequency higher than the line frequency in such j rr ~
-, - '- ' ~ . ' ~ , . , ^` 1C~84~94 manner that the time intervals of their ON states overlap cutting the switching device ON at the beginning of each half wave of A.C. line voltage, at least approximately at a phase angle of 0 , and cutting the power switching device OFF at a phase angle corresponding to the desired current flow angle; whereby the alternate connection of the transistors takes place in each half period of the A.C. line voltage beginning at its start and lasting until the desired cuTrent flow angle is reached.
According to another aspect of the present invention, there is provided a method of polarity-independent reduction of feedback from a consuming means periodically connected to an A.C, line which includes disconnecting the consuming means from the line during a predetermined period in each half wave of the A.C. line voltage, the improvement including damping and dis-charging the consuming means during each half wave of the A.C, line voltage using a power switching means during the predetermined period when the consuming means is disconnected from the A.C, line.
Further applications of the invention are possible in the field of electrical ignition for combustion processes.
Practical examples of the inventive method and of circuit arrangements for its performance will no~ be described in more detail with reference to the accompanying drawing, in which:
Fig. 1 is a diagram of current plotted against time in a consumer when using the known method of regulation by phase angle control, - llA -jrr:~rc .
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Fig. 2 is a diagram of the current plotted against time in a consumer when using the inventive method o~ regulation, Fig. 3 is a circuit diagram of a first practical form of the power switching device for performing the inventive method, ~ig~ 4 is a diagram of the control voltages as a function of time i~ respect of the power switch-ing device of fig. 3, Fig. 5 i~ a circuit diagram of a second practical form - of the power switching device, Fig. 6 i~ a diagram of the current consumption plotted with respect to time in a consumer with periodic interruption of the consumer from the alternating current network and respective reconnection of the consumer with the network, when the consumer has stored electrical energy, i.e. in the case of a complex consumer, Fi~. 7 is a diagram of the voltage established at a complex consumer plotte~ as a function of time, : Fig 8 i8 a diagram of the voltage established at a complex consumer plotted as a ~unction with - respect to time when using a variant of the inventive method, 12.
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Figo 9 is a circuit diagram of an arrangement for regulating the brilliance of a lighting installation having a second power switching device for performin~ the variant o~ the met~od of the invention, Fig. 10 is a diagram showing the control pulses used i~ the arrangement of fig. 9 plotted with respect to time.
I~ fig. 1 there is shown as a function of time the current flowing through a consu~er according to a known method Or regulation by phase angle control. ~rom the first zero cross-over point tO up to a later time instant tl the rele~ant power switching device remains blocked, i.e. no current flows.
At the time instant tl the power switching device is switched on, i.e. the consumer is connected to the network, so that a sudden current increase takes place at a high velocity, which c~uses the already described current peaks and high frequency disturbances to occur. The current continues to flow until the next zero cross-over point tO'.
` Fig. 2 show~ the correspo~ding current graph with respect to time in a method of regulation in accordance with the invention. ~he appertaining power switching device is here already switched on at the time instant tO of the first zero cross-over point, so that the network alternating current already flows through the consumer from the instant o~ c~oæs-f 13- i ~ }
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over of the alternating voltage, and the sudden ~rrent surge is avoided. At a later time instant t2, corresponding to the desired current flow angle, the power switching device i8 blocked so that the current flowing through the consumer sinks to zero until the power switching device is again switched on at the next zero transit.
In the practical e~ample represented in fig. 3 a consumer V is connected through a power switching device L~l to terminals N of an alternating current network. The power switching device ~Sl comprises two transistors Tl and '~2, which are mutually decoupled in parallel connection in that the~ respective collectors and emitters are connected together. The connected collectors and emitters of the transistors Tl and T2 are conneçted across one diagonal of a rectifier bridge Gl, which has in each branch a rectifier Dl, D2, D3 and D4 respectively, for example one or more diodesO
~he other diagonal of the rectifier bridge i8 connected in series with the consumer V. ~he rectifier bridge serves the purpose of protecting the transistors from faulty poling and to make possible the full-wave operation of thé power switching device here shown.
For the purpose of controlling th~ tra~sistthrs ~ and ~2 the bases thereof are connected in each case / a current limiting resistance Rl and ~2 to the secondary wind~ng of a .
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~ ~ f`` - ` 1084994 driver transformer TRl and TR2 respectively. To the primary windings of the respective transformers there are delivered control voltages Ul and U2, which will be further described herein, ~or which purpose the primary windings are connected to ~eparate output terminals of a control voltage generator SGl.
The control of the transistors ~1 and T2 throu~h the trans-formers makes it pos~ible by the use of impedance matching to keep the necessar~ control power low; this method of control also makes possible a potential separation of the bases of the two transistors. In~tead of using two transistors Tl a~d ~2 it i8 also possible, in accordance with the loading, to pro~ide a greater number of transistors connected in parallel in the same manner.
With the object firstly of obtaining precise switching instant~ for the transistors Tl and T2, and thereby to achie~e a precisely determined current flow angie, and secondly in order to keep the dimensions of the driving tr~nsformers ~Rl ~nd TR2 small, the control voltage generator SGl i8 80 designed that it delivers at it~ output terminals control signals, the frequency of which is substantially higher than that of thé
network frequency, and amounts for example to around 10 k~z.
~he con~trol signals are also preferably ~t least approximately rect~ngul~r, whilst the control signals delivered at the two respecti~e output pairs of terminals of the control signal generator SGl are mutually displaced in time but overlap each other.
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The control ~oltages Ul and U2, which are preferabl~
delivered by the control voltage generator SGl, are represented schematically in fig. 4 as a function of the time.
~he control voltage Ul is a re~tangular voltage with gating pulses I and spacing intervals L, in which the control voltage falls to zero value~ However, within the space intervals L
there are provided~ additional pulses Z, the polarity of which' is opposite to those of the gating pulses I. The control voltage U2 exhibits the same time characteristic as the control voltage Ul, but i8 time displaced with respect to it so that the gating pulses I of the control voltage U2 occur at the same time as the space intervals L of the control voltage Ul. As will be seen from fig. 4 the gating p~lses I of the control voltages Ul and U2 overlap ~ach other during the time period ~t.
~ he mode of operation of the power switching device of-fig. 3 i8 as follows, assuming as a basis the signal voltages ~1 and U2 of fig. 4.
At the beginning of a half-wave of the ~etwork altern~-ting voltage (phase angle e~ual to zero degree~) the control ~ generatorvoltage'~Gl i8 opened and delivers control voltages Ul and U2 to the primary windings of the driving transl'ormers TRl and TR2 respectively. Initially there is delivered through the one transformer, e.g. the transformer ~1, the control voltage Ul, with the gating pulse I, to the transistor ~1, so that the latter becomes current don'ducting. Before the beginning of the 16.
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saturation of the tra~sformer T~l the gating pulse I of the control voltage U2 is delivered by transformer TR2 and brings the transistor T2 into the current conducting condition, and indeed this happens during the time that the transistor Tl i8 still current conducting on account of the overlapping of the control voltages Ul and U2, so that in the consumer V there i~
obtained a continuous current flow. The space interval L
of the control voltage Ul now blocks the transistor ~1, whilst the additional pul~e Z of reverse polarity occurring within that interval removes the remanent mag~etization in the transformer, and thus increase~ the power capability for the next succeeding current conducting phase of the transistor ~1.
This operation repeats itself alternately for the transistors Tl and ~2, 80 that the loading distributes itself uniformly over the two participating transistors Tl and T2, whilst the current flowing through the consumer V ass~mes continuously the course of the network alternating voltage in the respective half-wave. For achieving the de~ired current flow angle, the control voltage generator SGl is then blocked~at the correspon-ding phase angle of the half-wave, 80 that a fuxther control of the transistors ~1 and T2 into t e current conducting condition is omitted until the beginning of the next half-wave of the network alternating voltage. The diodes Dl to D4 of the rectifier bridge Gl here provide for the correct poling in accordance with the alternating sign of the half-waves.
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In an e~ample the pulse frequency of the control ~oltages ~1 and U2 was lO kHz, the voltage of the gated pulses +lOV, the voltage of the additional pulses -lO V, and the transforma-tion ratio of the transformers ~Rl and T~2 was 3 ~ l. The ,;"
~ generation of the control voltages Ul and U2 as well as the .~,.................................................................... .
adjustment of the desired current flow angle by the starting and bloc~ing of the control voltage generator SGl can quite easil~ be effected with ~nown means, in particular by means of digital circuit arrangements.
A further practical form Or the power switching de~ice, which is capable of switching a larger current and which generates a smaller thermal loss is represented in fig. 5.
In the power switching device LS2 here shown there are provided two arrangements o~ decoupled parallel connected transistors T3, T4 and T5, T6 respectively, ths control of which i~ effected, as in the practical example of rig. 3, by the individually allocated driving transformers TR3, TR4, TR5 and TR6, together with current limiting resistances R3, R4, R5 and R6. For achieving the correct poling for a full-wa~e d~i~ing operation, a rectifier D5 and D6 respectively, e.g. a diode, i8 connected in series to each arrangement T~3, TR4 and TR5, TR6 of parallel connected transistors. ~hese two series circuits are connected in parallel and are situated in the current path of the network in series with the consumer V, so that the current ~low directions of the arrange~ent~ of the transistors and the . ,, /
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1084~9 '` .
~ ' .
rectifier1 with reference to the network or consumer connection side of the said parallel circuit, are opposite to each other in the one branch and the other br~nch of the parallel circuit.
~he primary winding~ of the transformers TR3 to TR6 are connected to suitable output terminals of a control ~oltage generator SG2 *or delivering the appertaining control voltages U3, U4, U5 and U6 The course taken b~ the control voltages U3 to U6 aiffers from that of the control voltages U2 and ~3 of ~ig. 3 ~olely by reason of the fact that, in dependence upon thé existing polarity of the network alternating voltage, the control can be discontinued of that particular arrangement of transistors T3, ~4 or ~5, ~6 respectively which happens to be in the non-loaded condition.
In the practical example of fig. 5 thermal losses occur only at two rectifiers D~, D6. Moreover the current loading distributes itself over four transistors ~3 to T6.
! In the described methods and circuit arrangements it is conceded that at the t~me instant of disconnection any stored electrical or magnetic energy will cause transient oscillation ahd will be dissipated in the consumer. In such a case it is to be expected that a voltage pea~ will occur. Because in most cases the consumer load will include both inducti~e and capacitive components, it will also not be possible to avoid change~ of curre~t direction in the consumer. ~urthermore it is ~ecessary to have regard to parit~ between the electrical .' 19.
.~
~` 1084994 condition in the consumer and in the network when the current supply to the consumer iB renewed~ because otherwise it must be expected that additional current peaks will result.
In fig. 6 there is shown, on a basis corresponding to that of fig. 2, the time function of a current taken by a consumer from a~ alternating current network, wherein the consumer is connected to the network in each half-wave at the zero cross-over point of the network alternating voltage, i.e. at the time instants tO, t2, t4 etc, and/co~nected fro~
the network at a later time instant tl, t~, t5 etc. corres-ponding to the desired current flow angle. It can be shown that, in consequence of the storage of energy, strong current peaks will occur at each reconnection of the consumer ~th the network at the time instants tO, t2, t4 etc., as indicated in fig. 6. Such current peaks cause considerable high frequency disturbing voltages, and moreover place a load on the switch-ing device which is used for effecting the discon~ection and reconnection of the consumer with the network, the switching element of said switching device usually being in the form of a semiconductor arrangement which i8 sensitive to current a~d voltage peaks.
The cause of the voltage peaks of fig. 6 is shown in fig. 7, which indicates the corresponding time function o~ the voltage at the consumer. ~he consumer is disconnected from 20.
, ' :~ - -1~84994 the network at the time point tl. In consequence of energy storage, the voltage at the consumer then falls off, for example in accordance with the full line of the curve and tends to continue a course along the dashed line. Because, at the time instant t2, at the zero cross-over point of the net~rork alternating voltage a reco~nection of the consumer with the networ~ iæ established, the decay process must ~e interrupted and the voltage at the consumer must of necessity follow the network voltage. The corresponding surge in the consumer voltage indicated at the time instant t2 in fig. 7, from a value differing from zero value to a practically zero value in the zero cross-over point of the network alternating voltage, gives rise to the current pea~ shown in fig.6 at the time instant t2 as well as at the corresponding time instants t4 etc. at the beginn;ng of a new commutation phase.
According to a variant of the inventive method, at all of the time instants tl, t3~ t5 etc. or shortly thereafter, i.e. after the disconnection of the consumer from the network, the consumer i8 damped a~d its energy content substantiall~
short circuited. ~he mode of operating this method i8 shown in fig.8. From this it ls clear that, as a result of the imposed damping and discharge beginn~ng from the time i~stants tl, t3, t5 etc., the voltage assumes a strongly attenuated course, so that at the time insta~ts t2, t4 etc., at which the consumer is reconnected to the network, the voltage has f 21.
-"` 108~994 practicall~ assumed the zero value. The current taken by the consumer from the network therefore no longer exhibit~
the current peaks at the time instants t2, t4 etc. shoh~ in fig.6, but in other respects t~kes the form of fig.6.
In fig. 9 there is shown schematically an arrangement for regulating the brilliance of a lighting installation. In this arrangement the consumer, which is conn~cted through a f~r~t power switching device to the terminals ~ of an alternating current network comprises a plurality of ballast devices V& and a pluralit~ of fluorescent tubes I~, of which only one of which i8 shown in the drawing, as well as the appertaining glow starter GS. ~he first power switching device is the same as the ~ower switching device LSl of fig.3 and therefore contains the rectifier bridge Gl with the four diodes Dl to D4 and the two transistors T1 and ~2, whose respectively connected collectors and e~itters are connected to one diagonal of the rectifier bridge Gl. ~he other diagonal i8 connected through two windings Wl and W2 of a choke D~ in series to the above mentioned con~umer. The choke windings Wl and W2 together with the parallel connected condensers Cl and C2 fu~ction both as disturbance protective members as well as protective means for the sem~conductor elements present in the illustrated arrangement.
For the purpose of controlling the transistors Tl and ~2, the ~ases thereof ar~, like those in fig. 3, connected 22.
1~84994 through current limiting resistances Rl, R2 and driving trans~ormers ~Rl, TR2 to a con~rol voltage generator SG3, which delivers the control voltages Ul and U2. The graph o$
the control voltages ~1, U2 has already been described with reference to fig.4 and is again shown in fig.10.
A second power switching device for periodically damping and discharging the consumer contains, according to fig.9, a ~urther rectifier bridge G2 with four diodes ~7 to D10, one diagonal of which rectifier bridge is connected through a limiting and load resistance R7, as well as through a further winding W3 of the choke D~, parallel to the consumer containing the ballast devices YG and the fluorescent tubes ~R. I~ the other diagonal of the rectifier bridge G2 there is connected the collector-emitter path of a Darlington transis-tor T7, whose base i8 connected through a current limiting resistacce R8 to the secondary winding of a further driving transformer TR7. ~o the primary winding Or the tr~nsformer ~7 there i8 delivered a control voltage U7, for which purpose the ilatter is connected to further output terminals of the control voltage generator SG3. ~he control voltage U7, like the control voltages Ul and U2, i8 rectangular and has a sub-stantially higher frequency as compared with the network frequenc~. Preferably the control voltage U7 exhibits the ~ame shape and frequency as the control voltages Ul and U2, as is represented in fig.10, but the control voltage ~7 contains no i, , 23. `
108499~
additic-al pul~as of opposite polarity. As will be fieen in fig.10 and will be further described later, the control volta~e ~o~orator SG3 periodically delivers the control voltage U7 at times when there is no delivery of control voltage~ Ul and U2 from the control voltage generator SG3.
At the beginning of a half-wave of the network alternatin~ vol~age (phase angle equal to zero degrees corresponding to the time insta~ts tO, t2, t4 etc. in fig.8) the control voltage generator SG3 delivers the control voltages Ul and U2 to the primary windings of the driving transformers TRl and TR2, as is alread~ described with reference to fig. 3. For obtaining the desired current flow angle, the control voltage generator SG3 then interrupts, at the corresponding phase angle of the half-wave, corresponding to the time instants tl, t3, t5 etc. in ~ig. 8, the delivery of the control voltages Ul and ~2, 80 that a further control Or the transistors Tl and T2 into the current conducting condition is suspended until the beginning of the next half-wave. The diodes Dl to D4 of the rectifier bridge Gl provide in this case for the correct poling in correspondence with the alternating sign of the half-waves.
~ llowing for a slight delay taking into aocount the storage and discharge times of the semconductor eleme~ts, the control voltage generator SG3 delivers, following the last pulse of the control voltages ~1, U2, and within the same . .: : ..
1(~84~94 half-wave, the rectangular control voltage U? (fig.10) so that the Darlington transistor T7 becomes current conducting.
Because the pulse gap~ of the control voltage U7 are smaller than the storage time of the Darlington transistor T7, the current conducting condition o$ the transistor T7 is continuous.
~he time period during which the transistor T7 is in the conducting condition provides, throu B the rectifier bridge G2, i e. the diodes D7, D9 or D8, D10 according to the polarity of the respective half-wave, the load resistance R7 and the winaing W3 of the choke DR, a current path parallel to the consumer. Accordingly it is possible for the electrical energy stored in the consumer to diæcharge continuously through the Darlington transistor ~7, th;s being i~dicated in fig.9 by the condenser C3 shown in dashed lines indicating a compen-sating and parasitic capacitance.
: As is evident from fig.10, the control voltage generator SG~ interrupts the delivery of the contro} volta~e U7 shortly before the next zero cross-over point of the network alternating voltage, i.e. shortly prior to the instant whe~ the control voltage generator SG3 again brings the transistors Tl and T2 alternately into the conducting condition by mean~ of the control ~oltages Ul and U2.
In the reconnection of the consumer to the network after the completion of periodic separatio~ from the network, the ` 25.
, , , ' ' ~ ~ ~ ' '.
' : : .
- . , 1~84994 suppression of current peaks, which is effected by the described discharge of the complex consumer for the purpose of power regulation i8 indeed involved with losses, but the~e are nevertheless acceptable and are not signific~nt as co~- -pared with the achieved advantage of the avoidance of current peaks ~or example the arrangement represented in fig.9 may be for the regulation of a fluorescent tube lighting installa-tion, which is designed for a nominal current of 35 A, and which includes for complete compensation of the fluorescent tubes a parallel capacitan¢e of 450 microfarads. This capacitance will, in the most un*avourable case, be charged to ~ voltage of 300 V, 80 that for each half-wave an energy of 135 mWs i8 to be expended, because the residual component in the *orm of non-capacitively ~tored energy is dis~ipated through the ballast deYices and~the fluorescent tubeY. ~he total efficiency of the arrangement shown in fig.9 is there-fore degraded by only 1.7%.
~ he oontrol of the transistors Tl, T2, ~7 through trans-rormers makes it possible to maintain the necessary control power small by impeda~ce matching. Furthermore this method makes po~sible the potential separation of the bases of the transistors. ~he generation of rectangular control signals ~1, ~2, U7 having a substantially higher frequency than that of the network can, as shown, be effected by a single control vol-tage generator SG3, 80 that the latter can ~e of relatively ~imple design.
26.
.' . . . . .. . : ,- -. . . ~.; ' ~ ~ . ' -. .
' ~ . ' : , :
. .
.
Claims (20)
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. In a method of regulating electrical power supplied via a current path to at least one consumer in an A.C. network which involves setting desired current flow angle using a power switching device connected in the current path to the consumer, the improvement comprising providing as the switching device at least two transistors, connected in parallel and mutually decoupled, connecting collector-emitter leads of said transistors in the current path to the consumer, switching the transistors alternately at a switching frequency higher than the line freq-uency in such manner that the time intervals of their ON states overlap cutting the switching device ON at the beginning of each half wave of A.C. line voltage, at least approximately at a phase angle of 0°, and cutting the power switching device OFF at a phase angle corresponding to the desired current flow angle;
whereby the alternate connection of the transistors takes place in each half period of the A.C. line voltage beginning at its start and lasting until the desired current flow angle is reached.
whereby the alternate connection of the transistors takes place in each half period of the A.C. line voltage beginning at its start and lasting until the desired current flow angle is reached.
2. A method according to Claim 1, including driving the transistors from transformer means.
3. A method according to Claim 2, wherein said driving step comprises driving each transistor by a driving voltage having gating ON pulses and gating OFF pulses, said voltage being at least approximately a square-wave voltage, and said voltage having a portion within its gating OFF pulses whose polarity is opposite to that of the gating ON pulses, in order to make the remanence of the transformer ineffective.
4. A power switching device for regulating electric power delivered to at least one power consuming means in an A.C.
network, the device comprising at least one set of two tran-sistors having their respective collector-emitter leads con-nected in parallel to define a current path; rectifier means for providing A.C. line voltage with the correct polarity coupled in series with said consuming means and said transistors;
secondary winding means of transformer means connected in resp-ective base-emitter circuits of said transistors; and primary winding means of said transformer means connected to a source of switching voltages to produce driving voltage for the trans-istors.
network, the device comprising at least one set of two tran-sistors having their respective collector-emitter leads con-nected in parallel to define a current path; rectifier means for providing A.C. line voltage with the correct polarity coupled in series with said consuming means and said transistors;
secondary winding means of transformer means connected in resp-ective base-emitter circuits of said transistors; and primary winding means of said transformer means connected to a source of switching voltages to produce driving voltage for the trans-istors.
5. A power switching device according to claim 4, wherein said rectifier means comprise a bridge rectifier having two diag-onals provided to produce bidirectional operation, one diagonal of said bridge rectifier being connected in series with said power consuming means, said transistors having their respective collector-emitter leads connected to the other diagonal of said bridge rectifier,
6. A power switching device according to claim 4, wherein said at least one set of two transistors comprises two sets of two transistors connected in parallel and wherein said rectifier means comprise first and second rectifiers connected respectively in series with a respective one of said sets for providing bi-directional operation in series with the consumer, whereby current flow direction in the two sets of transistors and in the two rectifiers, relative to the line or consumer connection side of the parallel circuit in one branch of the parallel circuit is opposite to that in the other branch.
7. A power switching device according to claim 6, including consuming means, said consuming means being at least one elect-rical illuminating fixture,
8. A power switching device according to claim 6, wherein said source comprises a source of at least two substantially square-wave voltages displaced in phase with respective to one another and defining overlapping ON pulses.
9. A power switching device according to claim 4, wherein said source comprises a source of at least two substantially square-wave voltages displaced with respect to one another, defin-ing overlapping ON pulses, with intervals between ON pulses defining OFF pulses, and respective pulses superimposed within each of the OFF pulses and having a polarity opposite said ON
pulses.
pulses.
10. In a method of polarity-independent reduction of feedback from a consuming means periodically connected to an A.C. line which includes disconnecting the consuming means from the line during a predetermined period in each half wave of the A.C, line voltage, the improvement including damping and discharging the consuming means during each half wave of the A.C. line voltage using a power switching means during said predetermined period when the consuming means is disconnected from the A.C. line.
11. An improved method according to Claim 10 wherein said power switching means comprises at least one transistor, the collector-emitter leads of the transistor being located in a current path parallel to the consuming means, wherein said damping and discharging is effected by enabling the transistor to conduct during at least one portion of the time interval between a connection and reconnection of the consuming means with the A C. line, with a switching frequency higher than the A.C. line frequency, disconnection occurring during a period of time which is shorter than the charging time of the transistor.
12. An improved method according to claim 11, wherein said enabling step is effected by applying a driving voltage, at least approximately a square-wave voltage, to a control electrode of the transistor.
13. An improved method according to claim 12, including supplying said driving voltage via a transformer.
14. A power switching device for polarity-independent reduction of feedback from a conserving means which is periodically connected to an A.C. line, the improvement comprising at least one transistor having collector and emitter leads; a rectifier means for supplying voltage at proper polarity for the consuming means to the transistor; circuit means connected in series with said rectifier means and in parallel to said consumer means; and a transformer having its secondary winding connected to the base-emitter circuit of said transistor and its primary winding con-nected with a source of switching voltage for producing driving voltage for said transistor.
15. A power switching device according to claim 14, wherein said rectifier means comprise a bridge rectifier, one of whose diagonals is connected parallel to said consumer means and with the collector-emitter leads of said transistor connected to the other diagonal.
16. A power switching device according to claim 14, wherein said circuit means comprises an ohmic resistor and a choke.
17. A power switching device according to claim 14, including additionally line switching means for coupling said consuming means to the A.C. line, said switching means including addit-ional transistors, said additional transistors being connected via transformers to circuit means for producing respective driving voltages for all said transistors.
18. A power switching device according to claim 14, wherein said at least one transistor is a Darlington transistor.
19. A power switching device according to claim 14, wherein said consuming means is connected to the A.C. line via line switching means, said line switching means being connected to said consumer means via at least one protective choke.
20. A power switching device according to claim 14, includ-ing said consuming means, said consuming means being at least one illuminating fixture; and line switching means whose variable current flow angle begins in each half wave of the A.C. line voltage at least approximately at a phase angle of zero degrees of the A.C. line voltage.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CH11447/76 | 1976-09-09 | ||
| CH1144776A CH610453A5 (en) | 1976-09-09 | 1976-09-09 | |
| CH1323676A CH611751A5 (en) | 1976-10-19 | 1976-10-19 | |
| CH13236/76 | 1976-10-19 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1084994A true CA1084994A (en) | 1980-09-02 |
Family
ID=25708349
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA286,101A Expired CA1084994A (en) | 1976-09-09 | 1977-09-06 | Method and apparatus for regulating electrical power delivered from an alternating current network |
Country Status (11)
| Country | Link |
|---|---|
| JP (1) | JPS53101652A (en) |
| AT (1) | AT359168B (en) |
| AU (1) | AU511121B2 (en) |
| BR (1) | BR7705961A (en) |
| CA (1) | CA1084994A (en) |
| DK (1) | DK146107C (en) |
| FI (1) | FI772438A (en) |
| FR (1) | FR2364507A1 (en) |
| GB (1) | GB1567797A (en) |
| IT (1) | IT1084743B (en) |
| SE (1) | SE427313B (en) |
Families Citing this family (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2117192B (en) * | 1982-02-26 | 1986-01-02 | Transtar Limited | Lamp control circuit |
| JPS58191013A (en) * | 1982-04-30 | 1983-11-08 | Nec Corp | Ac stabilized power supply |
| GB2120869A (en) * | 1982-05-04 | 1983-12-07 | Gen Electric | Controlling the output level of an electrical power supply |
| US4528494A (en) * | 1983-09-06 | 1985-07-09 | General Electric Company | Reverse-phase-control power switching circuit and method |
| US4507569A (en) * | 1983-12-30 | 1985-03-26 | Conservolite, Inc. | Electrical control system and driver |
| US4728866A (en) * | 1986-09-08 | 1988-03-01 | Lutron Electronics Co., Inc. | Power control system |
| DK628788A (en) * | 1987-12-12 | 1989-06-13 | Insta Elektro Gmbh & Co Kg | BRIGHTNESS ADJUSTMENT CIRCUIT |
| US5583423A (en) | 1993-11-22 | 1996-12-10 | Bangerter; Fred F. | Energy saving power control method |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE1488323A1 (en) * | 1964-01-24 | 1969-04-10 | Te Ka De Fernmeldeapp Gmbh | Circuit arrangement for keeping an alternating voltage or an alternating current constant |
| FR1430606A (en) * | 1964-04-03 | 1966-03-04 | Heem V D Nv | Improvements relating to a stabilized direct current power supply |
| US3564394A (en) * | 1969-01-03 | 1971-02-16 | Power Control Corp | Chopper-type alternating current regulator employing amplitude sensor and zero crossing detector |
-
1977
- 1977-08-15 FI FI772438A patent/FI772438A/en not_active Application Discontinuation
- 1977-08-24 JP JP10147877A patent/JPS53101652A/en active Pending
- 1977-08-29 FR FR7726159A patent/FR2364507A1/en active Granted
- 1977-08-31 AU AU28394/77A patent/AU511121B2/en not_active Expired
- 1977-09-05 SE SE7709956A patent/SE427313B/en unknown
- 1977-09-06 CA CA286,101A patent/CA1084994A/en not_active Expired
- 1977-09-08 DK DK400277A patent/DK146107C/en not_active IP Right Cessation
- 1977-09-08 IT IT27385/77A patent/IT1084743B/en active
- 1977-09-08 BR BR7705961A patent/BR7705961A/en unknown
- 1977-09-08 AT AT645277A patent/AT359168B/en not_active IP Right Cessation
- 1977-09-09 GB GB37740/77A patent/GB1567797A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| FI772438A (en) | 1978-03-10 |
| SE427313B (en) | 1983-03-21 |
| AT359168B (en) | 1980-10-27 |
| ATA645277A (en) | 1980-03-15 |
| GB1567797A (en) | 1980-05-21 |
| DK146107C (en) | 1983-11-21 |
| FR2364507B1 (en) | 1983-05-20 |
| AU511121B2 (en) | 1980-07-31 |
| DK400277A (en) | 1978-03-10 |
| SE7709956L (en) | 1978-03-10 |
| FR2364507A1 (en) | 1978-04-07 |
| BR7705961A (en) | 1978-07-04 |
| DK146107B (en) | 1983-06-27 |
| IT1084743B (en) | 1985-05-28 |
| AU2839477A (en) | 1979-03-08 |
| JPS53101652A (en) | 1978-09-05 |
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